Some locomotives are beginning to utilize electrical storage power sources, such as batteries, for providing energy to propel the locomotive, instead of or in addition to fuel-powered engines. The electrical storage power sources may be more efficient, more reliable, quieter, and/or produce fewer emissions than diesel engines and other fuel-powered engines. For example, some locomotives may include electrical storage devices, such as lithium ion batteries, that provide electric current to one or more alternating current (AC) traction motors. The traction motors convert electric current into mechanical energy that is used to rotate wheels and/or axles of the locomotive. Relying on a single type of electrical storage device for powering all tractive loads and demands of a locomotive, however, may exert stress on the electrical storage device that reduces the efficiency and/or operational lifetime of the electrical storage device.
For example, certain elevated demand situations along the course of a trip, such as initiating movement of the locomotive from a stationary position, accelerating, motoring along an incline grade, and the like, may apply a greater load on the electrical storage device than other situations such as cruising, braking, and traveling along a decline grade. For large freight trains, for example, that can weigh in excess of thousands of tons, the large inertial forces present during such elevated demand situations results in significant electric current drawn from the electrical storage device. Supplying the electrical current to meet the large demands during such elevated demand situations may significantly deplete the current supply within the electrical storage device, reducing operational efficiency and reducing the available travel range before recharging. Furthermore, the stress exerted on the electrical storage device and the heat generated during the elevated demand situations may degrade the electrical storage device and/or associated components, reducing the operational lifetime of these parts before replacement.